Isolated Transient Neonatal Ascites in a Preterm Infant Born to a Mother with Mirror Syndrome: A Case Report

BACKGROUND Isolated fetal and neonatal ascites is uncommon and poses substantial diagnostic and management challenges due to its diverse etiologies, which may include genitourinary or gastrointestinal malformations, infections, cardiac anomalies, and genetic disorders. Mirror syndrome, or Ballantyne syndrome, is a rare maternal complication typically associated with hydrops fetalis and characterized by maternal edema that "mirrors" the fetus and placenta, often mimicking preeclampsia. Its occurrence in conjunction with isolated fetal ascites is exceptionally rare, making recognition and management complex. CASE REPORT A female infant was delivered at 32 weeks of gestation after progressive isolated fetal ascites had been detected on routine prenatal ultrasound. The mother developed generalized edema and rapid weight gain consistent with mirror syndrome but without hypertension or proteinuria. Extensive maternal evaluation, including TORCH screening and karyotyping, yielded unremarkable results. Postnatal investigations excluded gastrointestinal obstruction, cardiac anomalies, hematologic or metabolic disorders, and endocrinopathies. Whole-exome sequencing did not identify a genetic cause. The neonate required brief ventilatory support and underwent therapeutic paracentesis, which removed 450 mL of straw-colored fluid, resulting in rapid improvement without recurrence. Serial postnatal ultrasounds confirmed resolution of the ascites; the infant achieved full enteral feeding with normal growth parameters. The mother's symptoms also resolved shortly after delivery. CONCLUSIONS This case highlights the rare association between isolated fetal ascites and maternal mirror syndrome. When severe etiologies are excluded, conservative neonatal management with paracentesis and close monitoring can yield favorable outcomes. A thorough multidisciplinary approach is essential, and continued follow-up is warranted to identify any late-emerging conditions.